Catheter balloon having impregnated balloon skirt sections

ABSTRACT

A balloon catheter and a method of making a balloon catheter, having a balloon with a first layer and a second layer, the first layer having at least one impregnated section impregnated with a polymeric material compatible with a polymeric material forming the catheter shaft. At least a portion of the impregnated section is fusion bonded to the shaft. In a presently preferred embodiment, the impregnated section is adjacent to a section of the first layer which is not impregnated with the compatible polymeric material. The impregnated section provides improved bonding of the balloon to the catheter shaft while minimizing the effect of the bond on catheter performance characteristics such as profile and flexibility.

BACKGROUND OF THE INVENTION

[0001] This invention generally relates to medical devices, andparticularly to intracorporeal devices for therapeutic or diagnosticuses, such as balloon catheters. In percutaneous transluminal coronaryangioplasty (PTCA) procedures, a guiding catheter is advanced until thedistal tip of the guiding catheter is seated in the ostium of a desiredcoronary artery. A guidewire, positioned within an inner lumen of adilatation catheter, is first advanced out of the distal end of theguiding catheter into the patient's coronary artery until the distal endof the guidewire crosses a lesion to be dilated. Then the dilatationcatheter having an inflatable balloon on the distal portion thereof isadvanced into the patient's coronary anatomy, over the previouslyintroduced guidewire, until the balloon of the dilatation catheter isproperly positioned across the lesion. Once properly positioned, thedilatation balloon is inflated with fluid one or more times to apredetermined size at relatively high pressures (e.g. greater than 8atmospheres) so that the stenosis is compressed against the arterialwall and the wall expanded to open up the passageway. Generally, theinflated diameter of the balloon is approximately the same diameter asthe native diameter of the body lumen being dilated so as to completethe dilatation but not overexpand the artery wall. Substantial,uncontrolled expansion of the balloon against the vessel wall can causetrauma to the vessel wall. After the balloon is finally deflated, bloodflow resumes through the dilated artery and the dilatation catheter canbe removed therefrom.

[0002] In such angioplasty procedures, there may be restenosis of theartery, i.e. reformation of the arterial blockage, which necessitateseither another angioplasty procedure, or some other method of repairingor strengthening the dilated area. To reduce the restenosis rate and tostrengthen the dilated area, physicians frequently implant a stentinside the artery at the site of the lesion. Stents may also be used torepair vessels having an intimal flap or dissection or to generallystrengthen a weakened section of a vessel. Stents are usually deliveredto a desired location within a coronary artery in a contracted conditionon a balloon of a catheter which is similar in many respects to aballoon angioplasty catheter, and expanded to a larger diameter byexpansion of the balloon. The balloon is deflated to remove the catheterand the stent left in place within the artery at the site of the dilatedlesion. Stent covers on an inner or an outer surface of the stent havebeen used in, for example, the treatment of pseudo-aneurysms andperforated arteries, and to prevent prolapse of plaque. Similarly,vascular grafts comprising cylindrical tubes made from tissue orsynthetic materials such as polyester, expanded polytetrafluoroethylene,and DACRON may be implanted in vessels to strengthen or repair thevessel, or used in an anastomosis procedure to connect vessels segmentstogether.

[0003] In the design of catheter balloons, characteristics such asstrength, compliance, and profile of the balloon are carefully tailoreddepending on the desired use of the balloon catheter, and the balloonmaterial and manufacturing procedure are chosen to provide the desiredballoon characteristics. A variety of polymeric materials areconventionally used in catheter balloons. Use of polymeric materialssuch as PET that do not stretch appreciably consequently necessitatesthat the balloon is formed by blow molding, and the deflated balloonmaterial is folded around the catheter shaft in the form of wings, priorto inflation in the patient's body lumen. However, it can be desirableto employ balloons, referred to as formed-in-place balloons, that arenot folded prior to inflation, but which are instead expanded to theworking diameter within the patient's body lumen from a generallycylindrical or tubular shape (i.e., essentially no wings) that conformsto the catheter shaft.

[0004] A catheter balloon formed of expanded polytetrafluoroethylene(ePTFE) has been suggested. ePTFE is PTFE which has been expanded toform porous ePTFE which typically has a node and fibril microstructurecomprising nodes interconnected by fibrils. However, ePTFE has provendifficult to bond to balloon liner materials and/or to catheter shafts.One difficulty has been bonding ePTFE absent the use of adhesives whichcan increase stiffness at the bond site, and/or bonding pretreatmentswhich can cause decomposition of the ePTFE fibril structure.

[0005] It would be a significant advance to provide a catheter balloon,or other medical device component, with improved performance andbondability.

SUMMARY OF THE INVENTION

[0006] This invention is directed to a balloon catheter and a method ofmaking a balloon catheter, having a balloon with a first layer and asecond layer, the first layer having at least one impregnated sectionimpregnated with a polymeric material compatible with a polymericmaterial forming the catheter shaft. At least a portion of theimpregnated section is fusion bonded to the shaft. In a presentlypreferred embodiment, the impregnated section is adjacent to a sectionof the first layer which is not impregnated with the compatiblepolymeric material. The impregnated section provides improved bonding ofthe balloon to the catheter shaft while minimizing the effect of thebond on catheter performance characteristics such as profile andflexibility.

[0007] A balloon catheter of the invention generally comprises anelongated shaft having a proximal end, a distal end, at least one lumen,and at least a surface formed of a polymeric material, and a balloon ona distal shaft section with an interior in fluid communication with theat least one lumen of the shaft. The balloon has a proximal skirtsection bonded to the shaft, a distal skirt section bonded to the shaft,and first and second layers extending from the proximal skirt section tothe distal skirt section. At least one of the skirt sections of theballoon is formed at least in part by the impregnated section of thefirst layer fusion bonded to the shaft. In a presently preferredembodiment, the first layer has a proximal impregnated section at leastin part forming the proximal skirt section, and a distal impregnatedsection at least in part forming the distal skirt section. Preferably,end sections of the second layer are also bonded to the shaft, althoughthey are not impregnated. Thus, the proximal and distal skirt sectionsof the balloon are preferably formed in part by the end sections of thesecond layer, and in part by the impregnated sections of the first layerof the balloon. The proximal and distal impregnated sections of thefirst layer are preferably adjacent to one or more sections of the firstlayer which are not impregnated with the polymeric material impregnatedin the impregnated sections.

[0008] The impregnated section of the first layer of the balloon isimpregnated with a polymeric material which is compatible with thepolymeric material of the shaft, so that the impregnated sectionimproves fusion bonding between the first layer of the balloon and theshaft. In one embodiment, the bond between the shaft and the proximaland distal skirt sections of the balloon is sufficiently strong towithstand balloon inflation pressures of about 90 to about 300 psiwithout failing (i.e., without rupturing or ballooning at the site ofthe bond or allowing inflation fluid to seep through the ePTFE layer ofthe balloon). The term compatible should be understood to refer topolymeric materials which are fusion bondable together. Morespecifically, compatible polymeric materials bond together by chemicalbonds (i.e., covalent or hydrogen bonds), and preferably arethermodynamically miscible together. In one embodiment, the polymericmaterial impregnated in the first layer impregnated section (“thecompatible polymeric material”) is the same polymeric material as theshaft polymeric material. For example, in one embodiment, the compatiblepolymeric material and the shaft polymeric material are the same polymerand are selected from the group consisting of Nylon 12, polyether blockamide (PEBAX), polyurethanes, and copolymers thereof, and acrylonitrilebutadiene styrene (ABS). However, the compatible polymeric material isnot necessarily the same polymer as the shaft polymeric material. In oneembodiment, the compatible polymeric material is from the same family orclass of polymeric materials as the shaft polymeric material, so thatthe polymers will covalently bond together. For example, in oneembodiment, the compatible polymeric material is a nylon and the shaftpolymeric material is PEBAX, and thus the polymers are both from thefamily of polymers known as polyamides. In another embodiment, thecompatible polymeric material and the shaft polymeric material are fromdifferent polymer families, but will hydrogen bond together, such as,for example, polyurethane and PEBAX, or nylon and polyurethane.

[0009] In one embodiment, the compatible polymeric material is solublein an alcohol, unlike polymers such as nylon 12 which are not soluble inalcohol. For example, ELVAMIDE, available from Dupont, is athermoplastic polyamide soluble in alcohols including methanol, ethanol,2-propanol, and a mixture of these with water. Such alcohols are readilyavailable, and typically have a higher vapor pressure, lower toxicity,and lower cost than organic solvents commonly used for polymers such asnylon 12, and thus improve the manufacturability of the ballooncatheter.

[0010] Preferably, the one or more impregnated sections of the balloonfirst layer are located only at the regions of the balloon skirtsections. Thus, the impregnated sections typically have a shorter lengththan the length of the first layer which is not impregnated with thecompatible polymeric material. The combined length of the proximal anddistal impregnated sections of first layer is typically about 10 toabout 50% of the length of the first layer. In one embodiment, theimpregnated section(s) of the first layer has a length approximatelyequal to the length of the section(s) of the first layer bonded to theshaft. Consequently, the impregnated section(s) has minimal effect onballoon performance characteristics such as compliance.

[0011] The first layer is formed of a porous polymeric material which inone embodiment is selected from the group consisting of expandedpolytetrafluoroethylene (ePTFE), an expanded ultra high molecular weightpolyolefin such as expanded ultra high molecular weight polyethylene,porous polyethylene, porous polypropylene, and porous polyurethane. Inone embodiment, the porous material has a node and fibrilmicrostructure. The node and fibril microstructure, when present, isproduced in the material using conventional methods. ePTFE and expandedultra high molecular weight polyethylene typically have a node andfibril microstructure, and are not melt extrudable. However, a varietyof suitable polymeric materials can be used in the method of theinvention including conventional catheter balloon materials which aremelt extrudable. Preferably, ePTFE is formed into a balloon layer bybonding wrapped layers of the polymeric material together to form atubular member, and not by conventional balloon blow molding. Althoughdiscussed primarily in terms of the embodiment in which the first layerof the balloon comprises ePTFE, it should be understood that a varietyof suitable polymers may be used for the first layer.

[0012] In a presently preferred embodiment, the first layer is an outerlayer relative to the second layer, although the first layer mayalternatively be an inner layer relative to the second layer. In oneembodiment, the outer (e.g., first) layer extends beyond the ends of theinner (e.g., second) layer. Specifically, in one embodiment, the firstlayer has a proximal end section and a distal end section, extendingbeyond the inner layer and in contact with and bonded to the shaft. Theimpregnated sections of the outer layer extend along at least part ofthe end sections of the outer layer which are in contact with and bondedto the shaft. Although discussed primarily in terms of the embodiment inwhich the first layer formed of ePTFE or other porous polymer is theouter layer of the balloon, it should be understood that the balloon canhave one or more ePTFE layers forming an outer, inner, or middle layerof the balloon.

[0013] A balloon catheter of the invention can be configured for use ina variety of applications including coronary and peripheral dilatation,stent delivery, drug delivery, and the like.

[0014] A method of making a balloon catheter which embodies features ofthe invention generally includes positioning a distal section of acatheter shaft within a first tube forming a tubular inner layer of theballoon, the tubular inner layer being formed of an elastomeric polymerand having a proximal end section, and a distal end section. A secondtube forming a tubular outer layer of the balloon, formed of a porouspolymeric material, is positioned on an outer surface of the tubularinner layer, with a proximal end section and a distal end section of thetubular outer layer in contact with the catheter shaft and having atleast a portion impregnated with a polymeric material compatible withthe polymeric material of the shaft and adjacent to a section of theouter layer which is not impregnated with the compatible polymericmaterial. The inner tubular layer is preferably bonded to the shaftbefore the outer tubular layer is positioned therearound, although itmay alternatively be bonded to the shaft during the fusion bonding ofthe outer layer to the shaft. Thus, in one embodiment, prior topositioning the outer layer around the inner layer, heat is applied atthe proximal and distal end sections of the inner tubular layer, to meltthe shaft polymeric material and the polymeric material of the innertubular layer and fusion bond the proximal and distal end sections tothe catheter shaft. Then the outer tubular layer is positionedtherearound and heat similarly applied thereto to melt the shaftpolymeric material and the compatible polymeric material and fusion bondthe proximal and distal end sections to the catheter shaft.

[0015] Although discussed in terms of a preferred embodiment in whichthe fusion bond between the balloon and shaft is a heat fusion bond, thefusion bond may alternatively be a solvent fusion bond. In the heatfusion bonding, the polymeric materials are heated to an elevatedtemperature at or around the melting temperature(s) of the polymericmaterials, so that the polymers melt together. The elevated temperatureis typically within about 120° C. to about 250° C. of the meltingtemperature of the polymers. For example, in one preferred embodiment,the elevated temperature is about 170° C. or more for PEBAX, and about120° C. or more for polyurethane. Alternatively, the polymeric materialsare solvent fusion bonded together by solubilizing the polymers togetherin a solvent and evaporating the solvent.

[0016] The balloon catheter of the invention has an improved bondbetween the balloon and the catheter shaft due to the impregnatedsection of the first layer of the balloon. The impregnated sectionprovides a strong fusion bond, without requiring adhesives or polymersleeves, and thus minimizes disadvantageously large increases instiffness and profile at the bond. Moreover, the balloon of theinvention has a improved manufacturability. These and other advantagesof the invention will become more apparent from the following detaileddescription and accompanying exemplary figures.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is an elevational view, partially in section, of a stentdelivery balloon catheter embodying features of the invention.

[0018]FIG. 1A is an enlarged sectional view of the catheter shown inFIG. 1, taken within area 1A.

[0019]FIG. 2 is a transverse cross sectional view of the ballooncatheter shown in FIG. 1, taken along line 2-2.

[0020]FIG. 3 is a transverse cross sectional view of the ballooncatheter shown in FIG. 1, taken along line 3-3.

[0021]FIG. 4 is a transverse cross sectional view of the ballooncatheter shown in FIG. 1, taken along line 4-4.

[0022]FIG. 5 illustrates the balloon catheter of FIG. 1, with theballoon in an inflated configuration to expand the stent within thepatient's body lumen.

DETAILED DESCRIPTION OF THE INVENTION

[0023]FIG. 1 illustrates an over-the-wire type stent delivery ballooncatheter 10 embodying features of the invention. Catheter 10 generallycomprises an elongated catheter shaft 12 having an outer tubular member14 and an inner tubular member 16. Inner tubular member 16 defines aguidewire lumen 18 configured to slidingly receive a guidewire 20, andthe coaxial relationship between outer tubular member 14 and innertubular member 16 defines annular inflation lumen 22, as best shown inFIG. 2 illustrating a transverse cross section of the distal end of thecatheter shown in FIG. 1, taken along line 2-2. An inflatable balloon 24disposed on a distal section of catheter shaft 12 has a proximal skirtsection 25 sealingly secured to the distal end of outer tubular member14 and a distal skirt section 26 sealingly secured to the distal end ofinner tubular member 16, so that the balloon interior is in fluidcommunication with inflation lumen 22. An adapter 36 at the proximal endof catheter shaft 12 is configured to provide access to guidewire lumen18, and to direct inflation fluid through arm 38 into inflation lumen22. In the embodiment illustrated in FIG. 1, the balloon 24 isillustrated in a noninflated configuration, with an expandable stent 30mounted on the working length of the uninflated balloon 24 for deliveryand deployment within a patient's body lumen 32. In the embodimentillustrated in FIG. 1, the uninflated balloon 24 has a wingless, lowprofile configuration prior to complete inflation of the balloon. Thedistal end of catheter may be advanced to a desired region of thepatient's body lumen 32 in a conventional manner, the balloon 24inflated to expand stent 30, and the balloon deflated, to implant thestent 30 in the body lumen 32.

[0024] Balloon 24 has an outer layer 33 and an inner layer 34, extendingfrom the proximal skirt section 25 to the distal skirt section 26 of theballoon. In the embodiment illustrated in FIG. 1, the outer layer 33 ofthe balloon 24 has a proximal impregnated section 27 bonded to the outertubular member 14, and a distal impregnated section 28 bonded to theinner tubular member 16. The impregnated sections 27, 28 of the outerlayer 33, together with end sections of the inner layer 34 bonded to theshaft 12, form the proximal and distal skirt sections 25, 26,respectively. Thus, in the embodiment illustrated in FIG. 1, theproximal skirt section 25 is formed at least in part by a proximal endsection of the inner layer 34 which is bonded to the shaft outer tubularmember 14 and by the proximal impregnated section 27 of the outer layer33 which extends beyond the inner layer 34 and which is bonded to theshaft outer tubular member 14. Similarly, the distal skirt section 26 isformed at least in part by a distal end section of the inner layer 34which is bonded to the shaft inner tubular member 16 and by the distalimpregnated section 28 of the outer layer 33 which extends beyond theinner layer 34 and which is bonded to the shaft inner tubular member 16.

[0025] The length of the sections of each layer 33 and 34 of the balloon24 secured to the shaft to form the proximal and distal skirt sections25, 26 are preferably minimized. Thus, the proximal and distal skirtsections 25,26 preferably have a length about equal to the minimallength required to provide a suitably strong bond between the balloon 24and the shaft 12. The length of the proximal end section of the innerlayer 34 bonded to the outer tubular member 14 is about 1 to about 5 mm,and the length of the proximal end section of the outer layer 33extending beyond the inner layer 34 and bonded to the outer tubularmember 14 is typically about 1 mm to about 4 mm, preferably about 1 mmto about 2 mm. Similarly, length of the distal end section of the innerlayer 34 bonded to the inner tubular member 16 is about 1 to about 5 mm,and the length of the distal end section of the outer layer 33 extendingbeyond the inner layer 34 and bonded to the inner tubular member 16 istypically about 1 mm to about 4 mm, preferably about 1 mm to about 2 mm.

[0026] The impregnated sections 27, 28 of the outer layer 33 of theballoon 24 are impregnated with a polymeric material 40 compatible withthe polymeric material of the outer and inner tubular members 14, 16.Although the distal impregnated section 28 is impregnated with the samepolymer 40 as the proximal impregnated section 27 in the embodiment ofFIG. 1, in an alternative embodiment (not shown), the distal impregnatedsection 28 is impregnated with a different polymer than the polymer 40impregnated in the proximal impregnated section 27. In the embodimentillustrated in FIG. 1, the outer and inner tubular members 14, 16 areeach formed of a single-layered, uniform polymeric member. However, itshould be understood that in alternative embodiments, one or both of theouter and inner tubular members 14, 16 may be a multilayered or blendedpolymeric member. The compatible polymeric material 40 is notnecessarily compatible with all the polymers forming parts of the shaft.Thus, the shaft has at least a surface formed of a polymeric material,and the compatible polymeric material 40 is compatible with saidpolymeric material forming the surface of the outer and inner tubularmembers 14,16 to which the impregnated section is bonded.

[0027] The compatible polymer 40 impregnated in sections 27,28 of outerlayer 33 facilitates fusion bonding the outer layer 33 of the balloon 24to the shaft 12. In one embodiment, the compatible polymer 40 is thesame polymer as the polymeric material of the shaft 12, for superiorfusion bonding, and is selected from the group consisting of nylon,PEBAX, and polyurethanes. In another embodiment, the compatiblepolymeric material and the shaft polymeric from the same polymer family,and are selected from the group consisting of polyamides (e.g., nylon12, PEBAX, and Elvamide), and polyurethanes (e.g., Pellethane andTecothane). The compatible polymeric material 40 may be the same polymeras, or a different polymer than, the polymeric material forming theinner layer 34 of the balloon. In a presently preferred embodiment, theinner layer is formed of a polymeric material compatible with thepolymeric material of the shaft 12, to facilitate fusion bonding oflayer 34 to the shaft 12.

[0028] Preferably, the outer layer 33 and inner layer 34 of the balloon24 are fusion bonded directly to the outer tubular member 14 and theinner tubular member 16 of the shaft 12, without an adhesive or separatepolymer layer between the layers 33, 34 and the shaft 12. Alternatively,in one embodiment, an adhesive or a separate polymer member is used tofacilitate bonding at least the inner layer 34 to the shaft 12.Conventional adhesives such as light-cured (e.g., Dymax 204) andcyanoacrylates (e.g., Loctite 4011) may be used to bond inner layer 34to the shaft 12. It should be understood that the surface of outer layer33 in contact with and directly fusion bonded to the shaft 12 may havebeen provided with surface treatments or other pretreatments, forenhancing the bondability of materials such as ePTFE.

[0029] In the embodiment illustrated in FIG. 1, the impregnated sections27, 28 extend only along the portions of the outer layer 33 which are incontact with and directly bonded to the shaft. Thus, the distal end ofthe proximal impregnated section 27 is located at the proximal end ofthe inner layer 34, and the proximal end of the distal impregnatedsection 28 is located at the distal end of the inner layer 34. In analternative embodiment (not shown), the distal end of the proximalimpregnated section 27 is located distal to the portion of the outerlayer 33 in contact with and directly fusion bonded to the outer tubularmember 14, and the proximal end of the distal impregnated section 28 islocated proximal to the portion of the outer layer 33 in contact with andirectly fusion bonded to the inner tubular member 16. Preferably, theimpregnated sections 27, 28 of the outer layer 33 of the balloon 24 donot extend into a portion of the outer layer 33 located between theproximal and distal skirt sections 25, 26 of the balloon.

[0030] The impregnated sections 27, 28 of the outer layer 33 areadjacent to a section of the outer layer 33 which is not impregnatedwith the compatible polymer 40. Thus, the impregnated sections 27, 28 ofthe outer layer 33 do not extend the entire length of the outer layer33, and preferably have a combined length which is less than the lengthof the section of the first layer which is not impregnated with thecompatible polymeric material 40. The section of the outer layer 33which is not impregnated with the compatible polymer 40 includes thecentral working length of the balloon 24 on which the stent 30 ismounted. In the embodiment illustrated in FIG. 1, the central section ofthe outer layer 33 is not impregnated with the compatible polymer 40 orwith another polymer, apart from being bonded to inner layer 34 whichmay at least partially fill some of the pores of the porous outer layer33. However, it should be understood that all or part of the sections ofthe outer layer 33 which are not impregnated with compatible polymer 40may be impregnated with a polymeric material different than thecompatible polymer 40.

[0031] The length of the proximal impregnated section 27 of outer layer33 is typically about 5 to about 20%, preferably about 5 to about 15% ofthe length of the outer layer 33, and the length of the distalimpregnated section 28 of outer layer 33 is typically about 5 to about20%, preferably about 5 to about 15% of the length of the outer layer33. Specifically, in one embodiment, the length of the proximalimpregnated section 27 of outer layer 33 is about 1 to about 4 mm, andthe length of the distal impregnated section 28 of outer layer 33 isabout 1 to about 4 mm, for a balloon 24 having a length of about 8 toabout 60 mm and a nominal outer diameter of about 2 to about 18 mm.

[0032] In a presently preferred embodiment, the outer layer 33 comprisesa porous polymeric material, and preferably a microporous polymericmaterial having a node and fibril microstructure, such as ePTFE, and theinner layer 34 is formed of a polymeric material preferably differentfrom the polymeric material of the outer layer 33. Preferably, thelength of outer layer 33 in contact with inner layer 34 is bondedthereto, and preferably by heat fusion bonding. Inner layer 34 limits orprevents leakage of inflation fluid through the microporous ePTFE toallow for inflation of the balloon 24, and is preferably an elastomericmaterial to facilitate deflation of the balloon 24 to a low profiledeflated configuration. The elastomeric material forming layer 34 mayconsist of a separate layer which neither fills the pores nor disturbsthe node and fibril structure of the ePTFE layer 33, or it may at leastpartially fill the pores of the ePTFE layer 33. The inner layer 34 ispreferably formed of an elastomeric material, including dienes,polyurethanes, silicone rubbers, polyamide block copolymers, and thelike.

[0033] The ePTFE layer 33 is formed according to conventional methods,in which a sheet of ePTFE polymeric material is wrapped with overlappingor abutting edges to form a tubular body and then heated to fuse thewrapped material together. The sheet of polymeric material preferablyhas the desired microstructure (e.g., porous and/or node and fibril)before being wrapped on the mandrel. The sheet of ePTFE polymericmaterial is wrapped spirally along a length of the mandrel, or byfolding the sheet around the circumference of the mandrel so that thelongitudinal edges of the sheet extend in a substantially straight linealong the length of the mandrel, to form one or more layers, andpreferably about two to about five layers, of wrapped material. Themultiple layers of ePTFE are typically heated to fuse the layerstogether. The tube of ePTFE polymeric material is typically furtherprocessed by being stretched, sintered, compacted, and sintered again,to provide the desired properties such as the desired dimension, anddimensional stability (i.e., to minimize changes in length occurringduring inflation of the balloon). The completed ePTFE layer 33 is thenbonded to or otherwise combined with elastomeric liner 34 which in oneembodiment is already secured to the catheter shaft 12.

[0034] In a method of making a balloon catheter having a balloon with aninner layer and an outer layer, a distal section of catheter shaft ispositioned within a tubular inner layer 34 of the balloon, so that thedistal end of the outer tubular member 14 and the distal end of theinner tubular member 16 of shaft 12 are within the proximal and distalend sections of the inner layer 34, respectively. Heat is applied at theproximal and distal end sections of the inner tubular layer 34, to meltthe polymeric material of the shaft 12 and the polymeric material of theinner tubular layer 34 at least at the interface thereof, and fusionbond the proximal and distal end sections of the inner tubular layer 34of the balloon 24 to the outer and inner tubular members 14, 16,respectively. Specifically, in one embodiment, an inner tubular layer 34formed of polyurethanes (e.g., Pursil, and Tecoflex) or dienes such assynthetic diene rubber, and a shaft having at least an outer layerformed of polyamides or polyurethanes, with shrink tubing therearound,are heated by a laser to a temperature at or above the meltingtemperature of the polymers, and specifically to a temperature of about120 to about 250° C., and more specifically to a temperature of greaterthan or equal to about 120° C. for a polyurethane shaft and to atemperature of greater than or equal to about 170° C. for a PEBAX shaft.

[0035] A tubular outer layer 33 of the balloon 24, formed of a porouspolymeric material such as for example ePTFE, is positioned on an outersurface of the tubular inner layer 34, with aproximal impregnatedsection 27 of the tubular outer layer located proximal to the proximalend section of the tubular inner layer 34 and in contact with the outertubular member 14, and with a distal impregnated section 28 of thetubular outer layer 33 located distal to the distal end section of thetubular inner layer 34 and in contact with the inner tubular member 16.

[0036] The proximal and the distal impregnated end sections 27, 28 ofthe tubular outer layer 33 of the balloon are impregnated with apolymeric material compatible with the polymeric material of the shaft12. Specifically, a solution of the compatible polymeric material isapplied to the end sections of the outer layer 33 before or after thetubular outer layer 33 is positioned around the balloon inner layer 34and the catheter shaft 12. In one embodiment, with the outer layer inplace around the inner layer of the balloon, compatible polymer solutionis applied, as for example by dipping, pouring, or spraying, on an outersurface of the end sections of the outer layer, so that the solutionfills the pores of the porous polymeric material at the end sections ofouter layer 33. Alternatively, the end sections of the outer layer 33 ofthe balloon 24 are impregnated with the compatible polymeric materialsolution before being placed in position around the balloon inner layer34 and the shaft 12, as for example, by dipping the end sections of theouter layer 33 into the solution. A sufficient amount of solution isapplied to saturate the end sections of the outer layer of the balloon,so that the solution fills the pores of the porous outer layer 33 and atleast some compatible polymer is at the inner surface of the outer layerafter evaporation of the solvent. In one embodiment, the amount ofsolution in the porous outer layer 33 is about 1 to about 20% by weight,for a porous outer layer 33 having a porosity prior to impregnation ofabout 80% to about 90%. In one embodiment, after impregnation, theporosity is about 65% to about 75%. The concentration of the compatiblepolymeric material solution is about 5 to about 40%, and preferablyabout 5 to about 15%, depending on the compatible polymer and the natureof the polymer forming the outer layer. In the embodiment in which thecompatible polymeric material solution comprises a common solvent suchas an alcohol such as methanol or ethanol, the concentration of thecompatible polymeric material solution is about 5 to about 40%, andpreferably about 5 to about 15%. After evaporation of the solvent, theamount of compatible polymer impregnated in the outer layer 33 istypically about 1 to about 20% by weight, preferably about 1 to about10% by weight of the outer layer 33.

[0037] The proximal and distal impregnated sections 27, 28 of thetubular outer layer 33 of the balloon 24 are adjacent to one or moresections of the outer layer 33 which are not impregnated with thecompatible polymeric material. The compatible polymer solution isprevented or inhibited from migrating beyond the end sections of theouter layer of the balloon and into the adjacent sections of the outerlayer of the balloon by a method involving masking the areas. In oneembodiment, at least the majority of the compatible polymer solutionremains where applied at the end sections of the outer layer 33. In oneembodiment, some of the solution may migrate beyond the end sections ofthe outer layer of the balloon into the adjacent sections of the outerlayer 33.

[0038] The proximal and distal impregnated sections 27, 28 of thetubular outer layer 33 of the balloon 24 are heated as set forth above,to melt the shaft polymeric material 12 and the compatible polymericmaterial 40 impregnated in the outer layer 33, and thereby fusion bondthe proximal and distal end sections of the outer layer 33 to thecatheter shaft 12. Specifically, the shaft and the impregnated sectionof an outer tubular layer formed of ePTFE impregnated with a polymersuch as for example polyamides (e.g., Elvamide) and polyurethanes (e.g.,Pellethane and Tecothane), with shrink tubing therearound, are heated bya laser, to a temperature at or above the melting temperature of thepolymers, and specifically to a temperature of about 120° C. to about250° C., to fusion bond the outer layer of the balloon to the shaft.

[0039] The resulting balloon catheter preferably has a rupture pressureof at least about 20 atm. During a medical procedure, the balloon istypically inflated to a working pressure of about 6 atm to about 25 atm,preferably about 6 atm to about 20 atm. The balloon is inflatable withinthe working pressure range without the skirt sections 25, 26 of theballoon 24 failing.

[0040] The dimensions of catheter 10 are determined largely by the sizeof the balloon and guidewire to be employed, the catheter type, and thesize of the artery or other body lumen through which the catheter mustpass or the size of the stent being delivered. Typically, the outertubular member 14 has an outer diameter of about 0.025 to about 0.04inch (0.064 to 0.10 cm), usually about 0.037 inch (0.094 cm), and thewall thickness of the outer tubular member 14 can vary from about 0.002to about 0.008 inch (0.0051 to 0.02 cm), typically about 0.003 to 0.005inch (0.0076 to 0.013 cm). The inner tubular member 16 typically has aninner diameter of about 0.01 to about 0.018 inch (0.025 to 0.046 cm),usually about 0.016 inch (0.04 cm), and a wall thickness of about 0.004to about 0.008 inch (0.01 to 0.02 cm). The overall length of thecatheter 10 may range from about 100 to about 150 cm, and is typicallyabout 143 cm. Preferably, balloon 24 has a length about 0.5 cm to about6 cm, and an inflated working diameter of about 2 to about 10 mm.

[0041] Inner tubular member 16 and outer tubular member 14 can be formedby conventional techniques, for example by extruding and neckingmaterials already found useful in intravascular catheters such apolyethylene, polyvinyl chloride, polyesters, polyamides, polyimides,polyurethanes, and composite materials. The various components may bejoined using conventional bonding methods such as by fusion bonding oruse of adhesives. Although the shaft is illustrated as having an innerand outer tubular member, a variety of suitable shaft configurations maybe used including a dual lumen extruded shaft having a side-by-sidelumens extruded therein. Similarly, although the embodiment illustratedin FIG. 1 is an over-the-wire stent delivery catheter, balloons of thisinvention may also be used with other types of intravascular catheters,such as rapid exchange dilatation catheters. Rapid exchange cathetersgenerally comprise a distal guidewire port in a distal end of thecatheter, a proximal guidewire port in a distal shaft section distal ofthe proximal end of the shaft and typically spaced a substantialdistance from the proximal end of the catheter, and a short guidewirelumen extending between the proximal and distal guidewire ports in thedistal section of the catheter.

[0042] While the present invention is described herein in terms ofcertain preferred embodiments, those skilled in the art will recognizethat various modifications and improvements may be made to the inventionwithout departing from the scope thereof. Moreover, although individualfeatures of one embodiment of the invention may be discussed herein orshown in the drawings of the one embodiment and not in otherembodiments, it should be apparent that individual features of oneembodiment may be combined with one or more features of anotherembodiment or features from a plurality of embodiments.

What is claimed:
 1. A balloon catheter, comprising: a) an elongatedshaft having a proximal end, a distal end, an inflation lumen, and atleast a surface formed of a polymeric material; and b) a balloon on adistal shaft section, having an interior in fluid communication with theinflation lumen of the shaft, and having a proximal and a distal skirtsection bonded to the shaft, and a first and a second layer extendingfrom the proximal skirt section to the distal skirt section, the firstlayer having at least one impregnated section impregnated with apolymeric material compatible with the polymeric material of the shaftand adjacent to a section of the first layer which is not impregnatedwith the compatible polymeric material, at least a portion of theimpregnated section being fusion bonded to the shaft.
 2. The ballooncatheter of claim 1 wherein the first layer of the balloon is an outerlayer relative to the second layer of the balloon.
 3. The ballooncatheter of claim 1 wherein the balloon proximal skirt section is formedin part by a proximal end section of the second layer of the balloonbonded to the shaft.
 4. The balloon catheter of claim 3 wherein the atleast one impregnated section of the first layer of the balloon is aproximal impregnated section having at least a portion which is locatedproximal to the proximal end section of the second layer of the balloonand which is fusion bonded to the shaft.
 5. The balloon catheter ofclaim 4 wherein the balloon distal skirt section is formed in part by adistal end section of the second layer of the balloon bonded to theshaft, and the first layer of the balloon has a distal impregnatedsection having at least a portion which is located distal to the distalend section of the second layer and which is fusion bonded to the shaft.6. The balloon catheter of claim 5 wherein the proximal and distalimpregnated sections of the first layer are heat fusion bonded to theshaft.
 7. The balloon catheter of claim 1 wherein the compatiblepolymeric material impregnated in the impregnated section of the firstlayer of the balloon is the same polymeric material as the shaftpolymeric material.
 8. The balloon catheter of claim 1 wherein thecompatible polymeric material impregnated in the impregnated section ofthe first layer of the balloon is different from a polymeric materialforming the second layer of the balloon.
 9. The balloon catheter ofclaim 1 wherein the compatible polymeric material impregnated in theimpregnated section of the first layer of the balloon and the polymericmaterial of the shaft are polyamides.
 10. The balloon catheter of claim1 wherein the compatible polymeric material impregnated in theimpregnated section of the first layer of the balloon is selected fromthe group consisting of polyamides, polyamide block copolymers, nylons,polyurethanes, polyurethane copolymers, and acrylonitrile butadienestyrene.
 11. The balloon catheter of claim 1 wherein the compatiblepolymeric material impregnated in the impregnated section of the firstlayer of the balloon is soluble in alcohol.
 12. The balloon catheter ofclaim 11 wherein the compatible polymeric material impregnated in theimpregnated section of the first layer of the balloon is a thermoplasticpolyamide.
 13. The balloon catheter of claim 1 wherein the polymericmaterial of the shaft is selected from the group consisting ofpolyamides and polyurethanes.
 14. The balloon catheter of claim 1wherein the impregnated section of the first layer of the balloon has alength less than a length of the section of the first layer which is notimpregnated with the compatible polymeric material.
 15. The ballooncatheter of claim 1 wherein the length of the impregnated section of thefirst layer of the balloon secured to the shaft is about 1 to about 4mm.
 16. The balloon catheter of claim 4 wherein the length of theproximal impregnated section of first layer of the balloon is about 1 toabout 4 mm.
 17. The balloon catheter of claim 4 wherein the length ofthe proximal impregnated section of first layer of the balloon is about5 to about 20% of the length of the first layer.
 18. The ballooncatheter of claim 5 wherein the combined length of the proximal anddistal impregnated sections of first layer of the balloon is about 5 toabout 50% of the length of the first layer.
 19. The balloon catheter ofclaim 1 wherein the amount of the compatible polymeric materialimpregnated in the first layer of the balloon is about 1 to about 20% byweight of the first layer.
 20. The balloon catheter of claim 1 whereinthe first layer of the balloon comprises expandedpolytetrafluoroethylene.
 21. The balloon catheter of claim 1 whereinfirst layer of the balloon is a porous material selected from the groupconsisting of expanded polytetrafluoroethylene, expanded ultra highmolecular weight polyolefin, expanded ultra high molecular weightpolyethylene, porous polyethylene, porous polypropylene, and porouspolyurethane.
 22. The balloon catheter of claim 1 wherein the secondlayer of the balloon comprises an elastomeric polymeric material. 23.The balloon catheter of claim 1 wherein the first and second layers ofthe balloon at the proximal and distal skirt sections are heat fusionbonded to the shaft.
 24. A balloon catheter, comprising: a) an elongatedshaft having a proximal end, a distal end, an inflation lumen, and atleast a surface formed of a polymeric material; and b) a balloon on adistal shaft section, having an interior in fluid communication with theshaft inflation lumen, and having a proximal and a distal skirt sectionfusion bonded to the shaft, an outer layer formed of expandedpolytetrafluoroethylene and an inner layer formed of an elastomericpolymeric material, the inner and outer layers extending from theproximal skirt section to the distal skirt section, each skirt sectionbeing formed of a section of the inner layer bonded to the shaft and atleast in part by an impregnated section of the outer layer bonded to theshaft, the impregnated section being impregnated with a polymericmaterial which is the same type of polymeric material as the shaftpolymeric material and adjacent to a section of the outer layer which isnot impregnated with the shaft polymeric material.
 25. A method ofmaking a balloon catheter, comprising: a) positioning a distal sectionof a catheter shaft having at least a surface formed of a polymericmaterial within a first tube forming a tubular inner layer of a balloon,the tubular inner layer having a proximal end section, and a distal endsection and being formed of an elastomeric polymeric material; b)applying heat at the proximal and distal end sections of the innertubular layer, to melt the shaft polymeric material and the polymericmaterial of the inner layer and fusion bond the proximal and distal endsections to the catheter shaft; c) positioning second tube forming atubular outer layer of the balloon on an outer surface of the tubularinner layer, with a proximal end section and a distal end section of thetubular outer layer in contact with the catheter shaft, the proximal andthe distal end sections of the tubular outer layer having at least aportion impregnated with a polymeric material compatible with thepolymeric material of the shaft and adjacent to a section of the outerlayer which is not impregnated with the compatible polymeric material;and d) applying heat at the proximal and distal end sections of theouter tubular layer, to melt the shaft polymeric material and theimpregnated compatible polymeric material and fusion bond the proximaland distal end sections of the outer layer to the catheter shaft.